Poebrotherium ( ) is an extinct genus of Camelidae, endemic to North America. They lived from the Eocene to Miocene epochs, 46.3—13.6 Annum, existing for approximately .[ Poebrotherium at fossilworks]
Discovery and history
Poebrotherium was first named by scientist
Joseph Leidy in 1848, and its relationship to other White River fossils was later expanded by him in 1853.
Fur trapper Samuel Culbertson was working in
Nebraska in pursuit of fur bearing mammals, and found a collection of strange fossil animal bones. He sent a box of these bones to his family back east, and not knowing what to make of them, they forwarded the remains to Leidy for identification.
Several animals' remains were included in this package, but one of the most interesting was that of a small mammal, about the size of a small deer or sheep. In addition to a partial skull, a portion of a forelimb was found. The portions that Leidy was able to examine helped him determine it was likely related to modern
, even though there was a paucity of new material available after his 1848 diagnosis.
This package spawned Leidy's interest in the White River badlands and its fauna, and he eventually sent collectors from the American Museum west to expand his collection. Between 1848 and 1853, cases of new material were shipping back to Leidy. Maddeningly, only three more
Poebrotherium tooth samples were among the remains recovered.
Etymology
The term
poebrotherium comes from (, "grass-eating")
and θηρίον (, "wild animal; animal; "beast"),
in Latinised form. The specific epithet is the Latinised name of a person or place, or a Latin adjective denoting a postulated characteristic of the species.
Species
-
Poebrotherium wilsoni can be translated as "Wilson's grass-eating beast".
-
Poebrotherium chadronensis can be translated as "grass-eating beast from Chadron formation".
-
Poebrotherium eximium can be translated as "Extraordinary grass-eating beast"
Description
Poebrotherium looked more like modern camels than its predecessor
Protylopus, but at in height, it was roughly the size of a modern
sheep. Its
skull resembled that of a modern
llama, while its limbs ended in
hoof toes and were more built for speed than the feet of
Protylopus. Despite this apparent adaptation to the open plains,
Poebrotherium has been found in all major White River environments, including forests and river overbank deposits, indicating that it was not tied to one particular environment.
The teeth of
Poebrotherium were more generalised than those of modern camelids.
In fact, despite the name meaning "grass-eating beast" it is likely that
Poebrotherium was either a browser or a mixed-feeder, and grass may have played a minimal role in the diet of
Poebrotherium.
Unlike its modern cousins, which are either adapted for desert or alpine conditions,
Poebrotherium took the place of a
gazelle or
deer in the White River Fauna ecosystem. This trait was taken to an extreme in later camels, notably
Stenomylus. Fossil evidence has shown that
Poebrotherium was a popular prey item for the
entelodont Archaeotherium. Remains of partial
Poebrotherium carcasses have been found fossilized, and appear to have been killed and cached by
Archaeotherium, the only animal known from the White River ecosystem that could have made the feeding marks found on the bones of
Poebrotherium.
Relationships
Poebrotherium lies within the
clade Camelidae, which can be defined as (
Stenomylinae + (
Miolabinae + (
Protolabinae +
Camelinae))) +
Poebrotherium. As such,
Poebrotherium lies outside the
Camelinae proper. In fact the definition of Camelidae is the most recent common ancestor of
Poebrotherium and
Dromedary, and all of its descendants.
Several authors offer characteristics to define Poebrotherium. These include a long neck; an adult height of around ; relatively unspecialized teeth; moderately long legs; long, unsplayed, unfused, and proximally wider-than-deep metapodials; a pes lacking digits 1, 4, and 5; and a typical ungulate stance but lacking in a foot pad.[Prothero, DR & RM Schoch (2002), Horns, Tusks, and Flippers: the Evolution of Hoofed Mammals. Johns Hopkins Univ. Press, 311 pp][Whistler, DP & SD Webb (2005), New Goatlike camelid from the Late Pliocene of Tecopa Lake Basin, California. Contrib. Sci. No. 503, 40 pp]
